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MANGANESE

Manganese is a chemical element with a symbol “Mn” is a free element found in nature. As a free element, manganese is a metal with important industrial metal alloy uses, particularly in stainless steels. Manganese is a pinkish-gray, chemically active element. It is a hard metal and is very brittle. It is hard to melt, but easily oxidized. Manganese is reactive when pure, and as a powder it will burn in oxygen, it reacts with water (it rusts like iron) and dissolves in dilute acids. Manganese is one of the most abundant metals in soils, where it occurs as oxides and hydroxides, and it cycles through its various oxidation states. The metal is reactive chemically, and decomposes cold water slowly. Manganese is widely distributed throughout the animal kingdom. It is an important trace element and may be essential for utilization of vitamin B. Manganese is most commonly produced by the reduction of the oxide with sodium, magnesium or aluminum. Alternatively it can be produced by electrolysis. One of the main ores of manganese is pyrolusite. Pyrolusite is made up primarily of the compound manganese dioxide (MnO2 ). Early artists were familiar with pyrolusite. They used the mineral to give glass a beautiful purple color. They also used the mineral to remove color from a glass.

PROPERTIES

It is gray-white, resembling iron, but is harder and very brittle. The metal is reactive chemically, and decomposes cold water slowly. Manganese is used to form many important alloys. In steel, manganese improves rolling and forging qualities, strength, toughness, stiffness, wear resistance and hardness. With aluminum and antimony, and especially with small amounts of copper, it forms highly ferromagnetic alloys. Manganese metal is ferromagnetic only after special treatment. The pure metal exists in four allotropic forms. The alpha form is stable at ordinary temperature; gamma manganese, which changes to alpha at ordinary temperatures, is said to be flexible, soft, easily cut, and capable of being bent. It has a specific gravity of 7.50.

CHEMICAL PROPERTIES

Manganese is a moderately active metal. It combines slowly with oxygen in the air to form manganese dioxide (MnO2). At higher temperatures, it reacts more rapidly. It may even burn, giving off a bright white light. Manganese reacts slowly with cold water, but more rapidly with hot water or steam. It dissolves in most acids with the release of hydrogen gas. It also combines with fluorine and chloride to make Manganese Difluoride (MnF2) and Manganese Dichloride (MnCl2).

USES

Manganese is essential to iron and steel production by virtue of its sulfur-fixing, deoxidizing, and alloying properties. The second large application for manganese is as alloying agent for aluminum. Aluminum with a manganese content of roughly 1.5% has an increased resistance against corrosion due to the formation of grains absorbing impurities which would lead to galvanic corrosion. Used as an additive in unleaded gasoline to boost octane rating and reduce engine knocking. The dioxide (pyrolusite) is used as a depolarizer in dry cells, and is used to "decolorize" glass that is colored green by impurities of iron.